After becoming reasonably good at welding, I discovered that I really needed higher amperage than the Lincoln 175 was giving me. Particularly for welding aluminum. I sold the Lincoln and bought a used Thermal Arc welder. Unfortunately it did not come with an Amptrol. So, rather than spending $150-250 to buy one, I spent 3-4 days making one.

	Ideally, I would have used gears to turn the potentiometer, but that would have meant spending money.. Also, I was too lazy to draw up a picture, so I made a couple mockups of the pulley arrangement first..		Since I didn't have a working lathe at the time, I made the pulleys on the RF40. Although getting everything lined up properly was a pain, actually making the pulleys was pretty straightforward.
			Here's the turning tool that I ground out of high speed steel for cutting the groove in the pulley.
			I made most of the pieces out of scrap metal I had laying around. The U bracket is a piece of square tubing with one face milled off.
			The piston is a piece of 1/2" drill stock with slots milled in either end.
	I used a piece of 2" square aluminum tubing cut in half for the side plates.
	I originally tried using steel picture-hanging wire to go between the pulleys but it proved too stiff.
	Ultimately I used nylon picture-hanging wire, although eventually I got some very fine throttle cable wire which worked very nicely.		This block is for the spring tensioning.
			The axle to hold the pedal-plate was hard to make because I used M6 screws in 3/8" stock which was hard to center on the mill.
	All assembled.		It we even works so far!
	I used a DB9 printer cable with one end chopped off for the signal wires. Here I'm soldering the leads to the pot.		I made a cable clamp from a piece of shim stock folded over so there were no sharp edges.
	Ready to weld!

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